1. Field of the Invention
This invention relates to crosslinked copolymers of vinylpyrrolidone (VP) and vinyl acetate (VA), referred to herein as "XL-PVP/VA", and more particularly, to strongly swellable, moderately crosslinked PVP/VA copolymers which are prepared directly as fine, white powders by precipitation polymerization of vinylpyrrolidone and vinyl acetate in an organic solvent.
2. Description of the Prior Art
Strongly swellable, moderately crosslinked polyvinylpyrrolidone (XL-PVP) was made by Shih, J., et al. in U.S. Pat. No. 5,073,614 by precipitation homopolymerization of VP in an organic solvent such as cyclohexane or heptane. However, it is desired to provide new and improved crosslinked polymers which are less hygroscopic and which exhibit enhanced mechanical properties, as compared to XL-PVP itself.
Accordingly, it is an object of this invention to provide a suitable process for making strongly swellable, moderately crosslinked copolymers of vinylpyrrolidone and vinyl acetate which are substantially non-hygroscopic and which have advantageous mechanical properties.
These and other objects of the invention will be made apparent from the following description of the invention.